1. Field of the Invention
This invention relates to a gunning apparatus and method for applying a refractory product in situ on the interior surface of a refractory body at an elevated temperature and more particularly to a nozzle assembly rotatably supported within the refractory body for rotation at a preselected speed in a preselected direction to apply the refractory product to a selected area of the interior surface.
2. Description of the Prior Art
The refractory bodies used in the iron and steel industry for carrying, holding and pouring of molten metal such as metallurgical ladles, blast furnaces, soaking pits, cupolas and the like are exposed to elevated temperatures over a long period of use that results in deterioration of the interior refractory surface. Consequently, the surface must either be periodically replaced or repaired. The interior surface may be repaired in a number of ways such as laying of refractory brick over the deteriorated surface. However, in order to reduce the labor costs of brick laying, the refractory industry has utilized high temperature plastic refractories having a pliable construction to permit shaping of the material to the contour of the interior surface being relined. The preshaped plastic refractory material is installed by pneumatic hammers to mold the refractory lining to the contour of the interior surface. It is also known to utilize a heat resistant castable cement refractory that is installed on the interior surface in a manner similar to the installation of conventional castable cement. This requires a substantial work force and the erection of frames to contain the castable refractory cement for curing.
More commonly the deteriorated surface of a ladle or blast furnace is reconditioned and repaired by the gunning application of a refractory material that is formed by mixing a dry mix of refractory binder and aggregate propelled through a hose by a stream of compressed air to a nozzle where a wetting agent, such as water, is supplied for mixture with the dry refractory to form a refractory product in a slurry. The refractory product is sprayed onto the interior surface. Typical of such gunning assemblies is the apparatus illustrated and described in U.S. Pat. No. 3,931,959. However, inherent with this method of gunning, as well as the above described methods, is the problem of cooling the ladle or furnace before the relining operation can be carried out. These methods require the installation personnel to work within the interior of the ladle or furnace; therefore, the surface to be relined must be allowed to cool prior to the relining operation. Thus, the ladle or furnace must be removed from operation to permit it to cool. This takes a considerable period of time which disrupts the steel making process, particularly when the relined ladle or furnace must be reheated to a preselected elevated temperature before restored to operation.
Lining guns for automatically spraying a refractory material upon the interior surface of a ladle or blast furnace, maintained at an elevated temperature, are well known as illustrated and described in U.S. Pat. No. 3,797,745. There a pair of concentrically positioned conduits separately supplies dry refractory material entrained in air and a wetting agent to a mixing nozzle where the wetting agent is mixed with the dry refractory material. The resultant refractory product is discharged from a pair of oppositely positioned nozzles onto the interior surface. The nozzle assembly is axially positioned within the ladle or furnace and the discharge nozzles are rotated as the assembly is moved from the bottom toward the top of the ladle to completely and entirely spray the interior surface. Because the relining operation is carried out at an elevated temperature the motor is subjected to the deleterious effects thereof resulting in malfunction. In addition the relining operation may require that only a portion of interior surface be relined with the refractory product as opposed to relining the entire interior of the ladle.
U.S. Pat. No. 3,799,445 discloses a remote-controlled refractory gunning apparatus that includes a mixing head having a refractory supply conduit connected to a swivel coupling by a water supply tee to which a water supply conduit is connected. A rotatable conduit extends downwardly from the swivel coupling and has a nozzle for spraying the mixed refractory and water onto the wall of a vessel to be relined. U.S. Pat. Nos. 2,785,008 and 2,858,836 disclose tank cleaning devices in which the former utilizes a reversible motor for rotating nozzle assemblies from which streams of liquid are discharged and the latter includes a nozzle head having a plurality of outlets that are oscillated in a vertical plane to spray only the top surface and upper end portion of a tank. Cleaning devices utilizing nozzles for directing a stream of fluid in a preselected direction are disclosed in U.S. Pat. Nos. 3,460,988; 3,420,444; 3,001,534; 2,858,836 and 2,082,330.
There is need to provide a gunning apparatus for applying a refractory product in situ upon the interior surface of a refractory body heated to an elevated temperature where the refractory product may be efficiently applied to a limited area of the interior surface as well as to the entire area of the interior surface.